Xylem SIT65 SATELLITE INTERNET TELEMETRY - Manual (Page 10)

Global Water Instrumentation
10
hours. Systems that require access to interrogation and control should have power
systems designed according to the requirements of the system. The voltage
thresholds for the different power modes are as follows:
Battery Voltage >= 12.8 volts; Battery Charging. The battery has sufficient charge
and the radio remains on all of the time to receive commands.
12.0 volts < Battery Voltage < 12.8 volts; Low battery. Radio remains on only
when data is being transmitted.
11.3 volts < Battery Voltage < 12.0 volts; Very Low Battery. Radio remains on
only when data is being transmitted. The SV LED blinks every 5 seconds
Battery Voltage <= 11.3 volts; Dead battery. All operations stop and the radio
remains shut off until the battery recharges again.
Battery Voltage Monitor
The SIT65 offers a full time battery voltage monitor that reports system voltage
automatically with every transmission. This is a very important tool for checking the
installation, system components, solar panels and battery. It should be watched
carefully when the system is first installed and periodically from then on. Downward
trends that seem abnormal may be an indicator that something is wrong. Sudden
changes in operation may be caused by environmental changes, an electrical
problem that is drawing excessive current, or a problem with the charging system. A
slowly dropping voltage may indicate that the battery is losing its capacity and needs
to be replaced. Other signs of this are that the problem will likely occur when going
into fall or winter, and that the size of the voltage fluctuations from day to night will be
larger than normal.
Solar Power Systems
The SIT65 systems are especially suited for very remote locations where solar
power is the only option. Solar powered systems require a very good understanding
of the application and system requirements. Some systems need to be powered
reliably all of the time and some can be shut down during the entire winter.
Availability of interrogation and control, transmission intervals, alarm transmissions,
the number of sensors connected, and many other factors must be evaluated. Most
importantly; seasonal changes and geographical factors like cloud cover,
temperature, snow, dust and how high the sun is in the sky can change solar system
efficiency. No attempt is made here to discuss all of the factors in solar system
design.